Lubricating apparatuses are traditionally designed as pumping units which are mounted in close association with respective cylinders and which are connected with a feeding reservoir for lubricating oil and with lubricating points in the form of oil injection nozzles at different points on the cylinder wall. Each pump unit includes a plurality of reciprocating pumps that feed various lubricating points with oil and which are driven by a common rotating control shaft with cams provided thereon. By the rotation of the shaft, the cams with pressing heads act on respective axially displacing pistons which are spring biased in direction towards the control shaft, so that the pistons at the rotation of the shaft will perform reciprocating movements for activating the pistons of the reciprocating pumps.
For many years, lubricating apparatuses have operated under the condition that the discharge pressure from the piston pumps was not to be very great, as it is a fixed standard that the oil is to be injected into the cylinder during the upwards return stroke of the engine piston, i.e. during the compressing action, however before the subsequent power stroke by the ignited combustion. Hereby, it has been necessary to operate with injection or pump pressures of the magnitude 10 bar.
In recent years it has been proposed to increase the efficiency of the lubrication by injecting the oil through pressurized atomizing nozzles for achieving oil mist lubrication during the upwards movement of the piston. However, hereby the oil is applied a far higher pressure for ensuring fine atomization through atomizing nozzles, e.g. a pressure up to 100 bar or more.
Furthermore, in recent years there has been a tendency that electronically based diesel engines are produced to a wider extent, and on these engines the mechanical drives traditionally used for driving mechanical lubricating apparatuses have been removed.
Lubricating points will thus, as mentioned in the present application, include oil injecting nozzles and/or pressurized atomizing nozzles.
In both systems, the control shaft is driven through a direct or indirect mechanical coupling with the crankshaft of the engine, whereby it is possible to provide power for the activation of pumps and at the same time to achieve synchronization between the crankshaft of the engine and the control shaft of the lubricating apparatus.
A pump unit may e.g. include a box-shaped apparatus housing, from where connecting pipes extend to the lubricating points on the associated engine cylinder, e.g. in a number of 6-24.
The pistons are traditionally operated by means of activation cams/rocker arms on a through-going control shaft which is rotated synchronously with the crankshaft of the engine. The pistons are spring biased towards the activation cams. There is provided a set screw defining the extreme position of an associated activation cam. The set screws may be operated for determining individual operative strokes of the pistons and thereby the associated yield of the individual piston pumps.
By lubrication according to the invention, it is possible for the user to operate with controlling injection timing for a synchronized lubrication, which is timed according to the rotation of the crank, or an unsynchronized cylinder lubrication, i.e. a cylinder lubrication that does not depend on the rotation and angular position of the crank.
Furthermore, there is an increasing demand for a flexible and easy adjusting of the controlled feeding cylinder lubrication oil portion for the immediate demand of the engine depending on diverse measurable engine parameters. It is also desirable to adjust the timing concurrently with the actual operating situation of the engine in a flexible way. All these adjustments are preferably to be controlled centrally.
Driving the lubricating apparatuses synchronously with the engine speed is electronically feasible, but extensive and costly. With such a system, the timing can be changed immediately. Changing the dosed cylinder lubricating oil portion is, however, more difficult to control.
As the cylinder lubricating oil is typically to be dosed with one portion per engine revolution, the only possibility of adjusting the dosage is to change the stroke of the pumps. A system for this purpose is e.g. described in DK patent application 4998/85. This system is operated by a cam disk mechanism for adjusting the pump stroke in dependence on the engine load. Changing this dependence may only be effected by replacing the cam disks with other cam disks with a different transfer function.
It has also been proposed to adjust the pump stroke by means of a controllable motor, e.g. a step motor. This has been used for point lubrication, but it is difficult to establish in connection with conventional lubricating apparatuses. Such a system is e.g. disclosed in International patent application WO 02/35068 A1.
Furthermore, from DE 28 27 626 there is known a lubricating system based on lubricating oil supplied in measured quantities for predetermined time intervals through openings in the cylinder wall. Here, there is not indicated any possibility of a stepless controlling of the dosing to be performed at the individual lubricating points.
Furthermore, from GB 834533 A, DK 173512 B1 or CH 673506 A5 systems of the type mentioned in the introduction are known, where a hydraulic cylinder via a distributor plate or similar structure acts on a plurality of dosing pistons. In these designs, there will be one hydraulic cylinder for the activation. This will cause disruption of operation for all dosing pistons if the hydraulic cylinder fails.
In connection with traditional cylinder wall lubrication, it has hitherto been the practice to use simple spring-biased non-return valves that can resist the internal pressure in the cylinder, but which yield to a slightly higher external injection pressure. However, in connection with pressurized atomized injection, it is desirable and necessary that the valve system opens only at a much higher oil pressure in order that the oil injection can assume the character of a pressurized atomizing injection right from the beginning. We are hereby speaking of a pressure differential factor of up to several hundred percent.
In DK patent application PA 2005 01629 it has previously been proposed with a hydraulically powered lubricating apparatus and a method for dosing cylinder lubricating oil of the type mentioned in the introduction. By the principle described in the mentioned patent application it is possible to establish the cylinder lubrication in a way so that there may be achieved a flexible electronic control and a central stepless control of the dosing to the lubricating points. Furthermore, there may also be attained precise and simple control of the timing.
This may be achieved by using a special setting unit with setting means engaging the dosing pistons and which is connected with a controllable actuator/motor for adjusting the setting unit.
It is possible to combine the technical effect from DK patent application PA 2004 01035, which describes an apparatus where regulation is performed by using a suitable number of valves for optional shutting off system oil to a dosing unit, with the technical effect of the present invention in order thereby to provide a system with two alternative possibilities for regulating the amount of lubricating oil.
The contents of the two above mentioned DK patent applications PA 2005 01629 and PA 2004 01035 are incorporated by reference.
The present invention may thus be used in connection with method and apparatus as described in the mentioned DK patent application.
However, the present invention may also be used in connection with other kinds of lubricating apparatuses and other methods where hydraulic lubrication using hydraulic pistons is applied for acting on injection units that include dosing pistons for the cylinder lubricating oil.